Freezing and refrigeration are the most common methods for keeping aquatic products fresh. The freezing temperature is low (-25-5 C). During the freezing process, ice particles formed by water in aquatic products expand in volume and destroy their structure, resulting in freezing denaturation. After thawing, water in aquatic products separates from the surface and dries, deteriorates the meat quality, and deteriorates the food sense. Although the structure of aquatic products has not been destroyed by refrigeration, for soft or crustacean aquatic products such as shrimp, crab, ink bucket, there are proteases in the meat. During the preservation process, the meat quality will appear white and turbid, the flavor will deteriorate, and the meat quality will become soft. At the same time, because of the high preservation temperature, microorganisms will multiply. Reproduction to inhibit, so the shelf life is only 3 days.
This paper introduces a new fresh-keeping method which can effectively inhibit the activity of protease, reduce the denaturation speed of protein and improve the shelf life, so that the fresh-eating aquatic products, especially the fresh soft and crustacean aquatic products, can still keep a high transparency and taste unchanged for a long time.
This is to impregnate aquatic products in a specific aqueous solution and then refrigerate them to improve the preservation effect. Sugar alcohols in specific aqueous solutions are 5%-40%. Sodium chloride 0.5%-10%, solid component concentration 5.5%-50%. The fresh aquatic products were soaked at 0 - 15 C for 1 minute - 48 hours and then stored at - 2 - 10 C.
Medical or food additive grade varieties should be selected for the use of sugar alcohols. Meanwhile, the average molecular weight of the selected sugar alcohols should be relatively low, water-soluble, not easy to crystallize and low in price. Among them, sorbitol, maltitol and reduced starch saccharide are the most ideal. When the concentration is between 5% and 40%, not only can the aquatic products keep good transparency, but also the viscosity is appropriate, and it is not easy to crystallize, and the economy is ideal.
The sodium chloride used is only food grade. The optimum concentration is 0.5%-10%. Under this concentration, the fresh-keeping effect of the preservative solution can be brought into full play.
It should be pointed out that the ratio of sodium chloride to sugar alcohol concentration should be kept in the range of 1:5-1:30, which can balance the saltiness and sweetness of the solution and is beneficial to its fresh-keeping function. If the proportion of sugar alcohol is low and the concentration of sodium chloride is high, the effect of preventing protein denaturation of aquatic products is not good, and the meat quality after preservation is easy to change color and turbidity; if the concentration of sugar alcohol is high and the concentration of salt is low, although it can keep the transparency of aquatic products high, the meat quality is soft and the sweetness is too strong, at the same time, sodium chloride is easy to precipitate. The result is not ideal.
The total concentration of glycol and sodium chloride should be 5.5%-50%, preferably 7%-20%. If the concentration is too low, the effective ingredients in the liquid can not fully penetrate into the inner tissues of aquatic products, and the effect is difficult to exert; if the concentration is too high, the surface of aquatic products will stick, and the sweetness itself will be too strong, which will affect the value of commodities.
There are many kinds of fresh-keeping aquatic products: shrimp, crab, cuttlefish, octopus, shellfish, shrimp and squid, etc.